The metadata below describe the original scanning. Follow the "All Files: HTTP" link in the "View the book" box to the left to find XML files that contain more metadata about the original images and the derived formats (OCR results, PDF etc.). See also the What is the directory structure for the texts? FAQ for information about file content and naming conventions.
Bibliography: List of the works by ... Haeckel that have been translated into English, p. 323-324; Complete list of Prof. Haeckel's works (exclusive of articles in scientific periodicals, etc.), p. 324-327